#include <stdio.h>

#define BUFSIZE 1000

void strcat2(char *s, char *t)
{
    char *p = s;
    while (*p) p++;
    while (*p++ = *t++);
}

int main()
{
    char s[BUFSIZE] = "Hello";
    char *t= "World";
    strcat2(s, t);
    printf("%s\n", s);

    return 0;
}